Experts say these situations don't come up often, but when they do, they need to be handled with an especially light touch. Rivals may be trying to draw you into a nasty public fight that could alienate your customers. Their advice: Avoid those kinds of showdowns, and don't try to be sneaky by posting anonymous comments of your own. Both approaches are likely to backfire.

Here's the smart way to handle the situation.

Be alert for signs a rival is hounding you.

In most cases, they'll simply cut and paste the same messages across multiple online venues. If they don't do that, they might use similar phrases from site to site, as well as the same links or photos. On forums, they might show up as a collusive gang of brand-new posters, without a track record on the site.

ENLARGE

Take your suspicions to site administrators.

Creating a fake identity for deceptive purposes—sockpuppeting—is against the terms of service at most forums and review sites, and most administrators will be willing to work with you. If the overseers can trace the posts back to a rival's Internet-protocol address, you can ask them to remove the posts, shut down fake member accounts or even—in extreme cases—block the IP address.

Once the posts are gone, follow up on forums to dispel any lingering suspicions.

You might provide company experts, for instance, who can clear up false claims. This is a vital step, since many forum messages will keep coming up in
Google
searches, especially when specific terms are mentioned. If you respond after the fact, you can get the truth on record.

If any of the attacks gain traction with concerned customers, supply a response in a Q&A on your website or social-network page.

But don't call attention to the false claims by referring to them directly. For instance, if a rival wrote falsely that your products are made in China, just make a point of saying that your goods are made in the U.S.

Whenever you counter claims, keep your tone helpful and neutral.

Don't be as nasty as the company that slammed you. Discussion sites can be very close-knit places with peculiar social dynamics. If you come in and sour the tone—particularly if you seem to have an agenda—users will get turned off.

Start early.

Before you run into trouble, establish a presence on forums and maintain goodwill there by answering questions without trying to give users a hard sell. If you build loyalty, users will be suspicious of random attacks on you and stick up for the company.

Mr. Nishi is a writer in Los Angeles. He can be reached at reports@wsj.com.

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